Chorus effects in electronic organ



Nov. 2, 1965 D. w. MARTIN CHORUS EFFECTS IN ELECTRONIC ORGAN Filed Jan. 25, 1962 lll .n.24 d im@ NmBon mnuozu L mm Pm INVENTOR DAm EL. MAZ-rm 921% m57- vl-L BY 2,

` ATTORNEYS United States Patent C) 3,215,767 CHORUS EFFECTS 1N ELECTRONIC ORGAN Daniel Wl Martin, Cincinnati, Ohio, assignor to D. H. Baldwin Company, a corporation of Ohio Filed Jan. 23, 1962, Ser. No. 168,104 7 Claims. (Cl. 84-1.24)

The present invention relates generally to systems for a-chieving ensemble effect in music by processing bands of audio frequency tones to introduce additional frequencies, and more particularly to systems for combining .plural tone generators with plural chorus generators in such manner as to achieve maximum ensemble effect.

It is well understood that musical tones maybe processed by continuous phase change modulators to provide new tone-s, the lspectra of the original and the processed tones being relatively displaced, so as to be wholly sharp or wholly flat, `one with respect to the other, or in part flat and in part sharp. Continuous phase changers, or frequency shift modulators, suitable for achieving the stated result are dis-closed in United States Patent 3,004,460, in the name of William C. Wayne, Jr., issued October 17, y1961. Such devices may be generally herein denominated chorus generators, because they have the effect of generating tones capable, when combined acoustically or electrically with unprocessed tones provided by tone generators, of providing chorus or ensemble effect.

It has been proposed to employ plural chorus generators in conjunction with a -single tone generator in an electronic organ, each chorus generator introducing different frequency shift-s from any other, in order to enhance the chorus effect achievable with a single chorus generator. 4It has also been suggested that an electronic organ having multiple tone generators may be provided with one or more chorus generators coupled to each of its tone generators. Since individual tone generators of the same nominal frequencies, of an electronic organ, are not phase locked to each other, and inevitably provide slightly different frequencies, itis thu-s feasible to provide, for example, six slightly different tones of a given nomenclature by means of three tone generators and three chorus generators.

In accordance with the present invention, plural tone generators are employed in conjunction with one or more Chorus generators, all the generators being connected to all the chorus generators. Thereby, each chorus generator is provided for processing with plural spectra, in response to tones of any single nomenclature, and provides plural spectra at its output. For example, if middle C is played, and contains a frequency f provided by tone generator G1, it will contain a frequency f-i-d provided by tone generator G2, in a two generator organ, where d may be plus lor `minus and of the order of 1 c.p.s. If these frequencies are applied to a single chorus generator which introduces a frequency shift Af, which may be plus or minus, the-output of the chorus generator will contain two frequencies, i.e. f-j-d-l-Af and -l-Af. Thereby, two tone generators and one chorus generator provide four different frequencies. By analogousA reasoning, two tone generators and two chorus generators provide six different frequencies, and in general m tone generators plus n chorus generators provide mtr-j-l) frequencies. Since chorus generators are in general less costly than tone generators, the musical effect of a large number of tone generators can be achieved at minimum cost by combining plural tone generators with one or more chorus generators.

' It is, accordingly, a broad object of the present invention to provide a system for simulating the effect of a multiple tone generator organ having a large number of generators, while utilizing a minimum number of such generators.

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'Itis a further object of the invention to provide a system comprising an electronic organ having plural tone generators and plural associated chorus generators, in which a maximum number of frequency displaced spectra is produ-ced for a minimum number of generators.

It is another object of the present invention to provide a 'system for achieving ensemble effect in music, employing an electroni-c organ having plural tone generators, in conjunction with at lea-st one frequency shift chorus generator coupled to all the tone generators.

A further object of the invention resides in the provision of a system for achieving ensemble effect in music, by combining plural tone generators with plural chorus generators, all the tone generators being coupled to all the chorus generators, to achieve a maximum number of distinct but congruent frequency spectra.

v The above and still further objects, features and advantages of the present invention will become apparent upon consideration of the following detailed description of one specic embodiment thereof, especially when taken in conjunction with the accompanying drawings, wherein the single figure of the drawings is a functional block diagram of a system according to the invention.

Referring now to the accompanying drawings, the reference numerals 10, 11, 12 denote tone generators, each generating continuously the gamut of the music tones appropriate to an electronic organ. The several tone generators 10, 11, 12 are independent of each other, and may be slightly detuned with respect to one another, so that any single tone generated simultaneously by all the tone generators, will have the fundamentals of that tone, as well as its partials, slightly frequency displaced with respect to one another. The fact is indicated by identifying the frequency f of tone generator 10, as f-l-d in generator 11 and as frequency f-g in generator 12, where d and g are of the order of 1 c.p.s. for middle C. Nevertheless, the precise relation among the several frequencies is not specified, and at minimum the several frequencies must be asynchronous, so that on acoustically transducing the tones an ensemble effect is achieved.

The tone generators 10, 11, 12 are connected via sets of leads 13, 14, 15 to sets of key operated switches 16, 17, 18, respectively. The latter may be operated individually by separate keyboards-for example, two manuals `and a pedal clavier-or they may be ganged so as to be responsive collectively to a single manual, as indicated by the mechanical coupling 29. Also, in accordance with the teachings `of a copending application of the same assignee, U.S. Serial No. 698,222, now Patent Number 3,049,959, in the name of Albert Meyer, iiled November 22, 1957, entitled Ensemble System Employing Multiple Generators, tone generators 10, 11 and 12 may be connected to different decks of key switches on the same keyboard in the sets represent-ed by the blocks 16, 17, or 18.

The key switches 16, 17, 18 channel selected tones from the tone generators 10, 11, 12 to sets of formant or tone color filters 19, 20, 21. The latter are selectable at will, in a manner conventional in the electronic organ art, by means of stops or tab switches, so that any tone selected .by any one or more of key switches 16, 17, 18 may be passed through anyone or more of the tone color lters 19, 20, 21. Each set of tone color lters 19, 20, 21 may provide filters appropriate to the footages employed. The separate tone color lters 19, 20, 21 may be connected to organ division pre-amplifiers 22, 23, 24,` respectively and to isolating networks 30, 31, 32.

The description of the system of FIGURE 1 is, to this` point, that of a conventional organ system, employing plural tone generators.

In accordance with the present invention, three chorus generators are employed to enhance the tones provided by the filters 19, 20, 21, although only one, or two, may be employed, without departing from the broad principles lof the invention. Chorus generators per se are described and illustrated in the aforementioned patent of William C. Wayne, to which reference is made. yFor Athe purposes of the present exposition, it is sufcient that chorus generators of the type specied are capable of displacing the several frequencies of a complex audio spectrum either positively or negatively, preferably on a percentage basis, so that each frequency of the audio spectrum is varied, either sharp or fiat. A suitable percentage range is .2 to .5%.

The -output of division pre-amplifier 22 is applied to an isolation network 30 having four parallel resistive branches, 30a, 30b, 30e and 30d. Similarly the output of the division pre-amplifier 23 is applied to an isolation network 31, having four parallel resistive branches 31a, 31h, 31e, 31d. Further, the output of division pre-amplifier 24 is applied to an isolating network 32 having four parallel resistive networks 32a, 32b, 32C, 32d.

The branches 30a., 31a, 32a are joined at their output terminals, to a common terminal 33, which connects to the input of power amplifier 34, the latter supplying a loud speaker 35. The latter radiates simultaneously the unmodified tonal outputs of all the division pre-amplifiers 22, 23, 24.

The branches 30h, 31b and 32b are connected to a common lead 36, which supplies signal to a chorus generator 37. The latter may introduce a frequency shift of -l-Afl c.p.s. into all tones supplied thereto. Its output drives a power amplifier 38, which in turn drives an acoustic radiator or loud speaker 39.

The branches 30e, 31C, 32C supply a chorus tone generator 40, which introduces a frequency shift of Afz, and drives a power amplifier 41, and speaker 42.

The outputs of branches 30d, 31d, 32d are combined on lead `45, which supplies signal to chorus generator 46, arranged to introduce a frequency shift of -Afs c.p.s. in all signals applied to its input. The -output of chorus generator 46 drives a power amplifier 47, and loud speaker 48.

The frequency shifts Afl, Afz and Afa may 'be fixed amounts, respectively, but they are preferably proportional to frequency; as in the range of percents mentioned above.

Describing now the operation of the present system, and assuming that tone generator provides a single frequency f to division pre-amplifier 22, while tone generators 11 and 12 supply each a single frequency, denoted f-l-d, f-g, respectively. These three frequencies are combined at terminal 33 and commonly radiated by speaker 35. Each of the frequencies f, -l-d, f-g is frequency shifted by a factor +Af1, in chorus generator 37. Accordingly, speaker 39 radiates frequencies f-l-Afl, f-|d-|Af1, f-g|-Af1. Each of the frequencies f, f--l-d, f-g is frequency shifted by an amount -I-Afz in chorus generator 40, whereby speaker 42 radiates frequencies f-i-Af2, f|d|-Af2, f-g-l-Afz. By similar reasoning speaker 48 radiates frequences f-Af3, f-l-d-Afa. f-g-Afa- 'Since each of the chorus generators 37, 40 and 46 provides three tones in ensemble, each is functionally the equivalent of three tone generators, such as 10, or 11, or 12. Thus the system as disclosed provides a total of twelve tones in ensemble, at a cost of three tone generators and three chorus generators.

The general principles of the invention can be extended to various numbers of tone generators and chorus generators, according to columns 1 and 2 of the following schedule, -which provides an effective number of tone generators according to column 3 of the schedule. In general for m tone generators and n chorus generators, a total number of ecective generators m\(n|1) can be achieved.

It will be obvious to one sk-illed in the art that the full chorus effects of this invention will not be realized unless a given note is played on both manual keyboards and on the pedal keyboard, or unless provision is made for obtaining from one key, signals from all available sources of the normal pitch corresponding to that key. This can be accomplished, for example, by mechanical couplers 29, as mentioned hereinabove. Also, it can be accomplished by the previously-mentioned Meyer system, wherein a given key may actuate a plurality of switches deriving signals from the corresponding sources in three tone generators, for example. The total number of acoustic radiators employed involves a matter of judgment. In the limit, all the tones may be radiated by a single radiator, or, as illustrated, each chorus generator may be provided with its individual radiator. One amplifier 34 and loudspeaker 35 may be used for the three mixed unshifted outputs. Or the outputs through resistors 30a, 31a and 32a may be separately amplified and radiated. It is musically preferable to utilize six radiators, one each for the chorus generator outputs, and one for each of the tone generators.

While I have described and illustrated one specific embodiment of the present invention, it will become apparent that variations of the specific details of construction may be resorted to without departing from the true spirit and scope of the invention as defined in the appended claims.

I claim:

1. In an electronic organ, a first tone generator providing a first gamut of musical tones having a first frequency spetcrum including a representative frequency f, a second tone generator providing a second gamut of musical tones having a second frequency spectrum including a representative frequency f-i-d, where f and f-i-d are at least relatively asynchronous and at least approximately equal, a chorus generator comprising an input circuit and an output circuit, said chorus generator being arranged to displace in frequency at said output circuit all the frequencies of a spectrum applied 'to said input circuit, and means connecting said first and second tone generators to said input circuit simultaneously.

2. In an electronic organ system, a plurality of tone generators, each of said tone generators being arranged to provide a gamut of musical tones having a frequency spectrum, the frequency spectra for the separate tone generators being musicaly distinguishable but congruent, a plurality of chorus generators each comprising an input circuit and an output circuit, each of said chorus generators being arranged to displace in frequency at its output circuits all the frequencies of a spectrum applied to its input circuit by different amounts for the separate chorus generators, and means connecting all said tone generators to all said input circuits of said chorus generators simultaneously.

3. The combination according to claim 2 wherein is provided a separate acoustic radiator connected to each of said output circuits.

4. The combination according to claim 2 wherein is provided a separate acoustic radiator coupled to each of said tone generators and said output circuits.

5. In an electronic organ system, a plurality of tone generators, each of said tone generators being arranged to provide a gamut of musical tones, the frequency spectra of the gamuts of musical tones being all musically distinguishable, a chorus generator, said chorus generator being arranged to provide at least one frequency shift of the frequency spectra applied thereto, an acoustic radiator, and means for connecting said tone generators in common to said chorus generator, and said chorus generator to said acoustic radiator and separate acoustic radiator means connected directly to said tone generators and by-passing said chorus generator for radiating separately the outputs of said tone generators and of said chorus generator.

6. In an electric organ, a first tone generator providing a first gamut of complex musical tones having a frequency f as the fundamental frequency of one tone of 20 said first gamut, a second tone generator providing a second gamut of complex musical tones having a frequency iid as the fundamental frequency of said tone of said second gamut, where claimed is a small frequency value of the order of several cycles per second, corresponding 25 tones of said first and second gamuts being separated in frequency by at least approximately the frequency increment d, a separate set of key operated switches in cascade with each of said tone generators, a first power amplifier,

means connecting said first and second tone generators 30 jointly to said first power amplifier via said key operated switches for amplification in a single channel of tones called forth by both sets of key operated switches, a first loud speaker connected in cascade with said first power amplifier, a chorus generator comprising an input circuit and an output circuit, said chorus generator being arranged to displace slightly in frequency at said output circuit all the frequencies of a frequency spectrum applied to said input circuit, means converting said first and second generators via said keys to said input circuit for displacement in frequency by said chorus generator of all the frequencies called forth by both sets of keys, and a second loud speaker connected to said output circuit.

7. The combination according to claim 6, wherein is further provided means for separately acoustically radiating the outputs of said tone generators and of said chorus generators.

References Cited by the Examiner UNITED -STATES PATENTS 2,305,574 12/ 42 Koehl.

2,498,367 2/50 Hammond et al.

2,547,759 4/51 Kent.

2,879,683 3/59 Martin 84-1.24 3,000,252 9/61 Wayne 84-1.01 3,004,459 10/61 Jones 84-1.01 3,004,460 10/61 Wayne 84-1.01 3,007,361 11/61 Wayne 84--1.0l 3,147,333 9/64 Wayne 84-1.24

ARTHUR GAUSS, Primary Examiner. CARL W. ROBINSON, Examiner. 

1. IN AN ELECTRONIC ORGAN, A FIRST TONE GENERATOR PROVIDING A FIRST GAMUT OF MUSICAL TONES HAVING A FIRST FREQUENCY SPETCRUM INCLUDING A REPRESENTATIVE FREQUENCY F, A SECOND TONE GENERATOR PROVIDING A SECOND GAMUT OF MUSICAL TONES HAVING A SECOND FREQUENCY SPECTRUM INCLUDING A REPRESENTATIVE FREQUENCY F+D, WHERE F AND F+D ARE AT LEAST RELATIVELY ASYNCHRONOUS AND AT LEAST APPPROXIMATELY EQUAL, A CHORUS GENERATOR COMPRISING AN INPUT CIRCUIT AND AN OUTPUT CIRCUIT, SAID CHORUS GENERATOR BEING ARRANGED TO DISPLACE IN FREQUENCY AT SAID OUTPUT CIRCUIT ALL THE FREQUENCIES OF A SPECTRUM APPLIED TO SAID INPUT CIRCUIT, AND MEANS CONNECTING SAID FIRST AND SECOND TONE GENERATORS TO SAID INPUT CIRCUIT SIMULTANEOUSLY. 